ACPV, Indian Agricultural Research Institute, New Delhi 110 012, India
Large cardamom (Amomum subulatum Roxb.) is affected by the serious disease ‘foorkey’, which is of unknown etiology (1). Excessive sprouting and formation of bushy dwarf clumps at the base of mother plants that gradually die, characterize the disease. In surveys in the Sikkim-Darjeeling Hill area during 2002 and 2003, as much as 27% of plants were found to be affected. Electron microscopy of negatively stained, partially purified preparations from field-infected large cardamom plants showed the presence of isometric particles measuring 17 to 20 nm. The causal agent was successfully transmitted by the aphid Micromyzus kalimpongensis Basu, in a persistent manner. Ten randomly selected field samples gave A405 0.1 to 0.23 compared with 0.57 with positive control with enzyme-linked immunosorbent assay using antiserum to an Indian isolate of Banana bunchy top virus (BBTV). A fragment of approximately 850 bp was amplified from the diseased plants using polymerase chain reaction (PCR) with primers 5′-ATGGCGCGATATGTGGTATGC-3′ and 5′-TCAGCAAGAAAACCAACTTTATTC-3′, designed to amplify the putative Rep gene based on the sequences of DNA1 of BBTV. The PCR product was cloned and sequenced (GenBank Accession No. AY 485960) and showed 80 to 82% identity with the corresponding region of DNA1 of BBTV and 47.6 to 48.5% with other recognized nanoviruses. These findings indicate that a nanovirus is associated with ‘foorkey’ disease of large cardamom, which is tentatively named as Cardamom bushy dwarf virus.
Reference: (1) P. M. Varma and S. P. Capoor. Indian J. Agric. Sci. 34:56, 1964.